1. Field of the Invention
The present invention is related to hip joint replacement surgery and in particular for correct positioning and implantation of an acetabular prosthetic socket. The present invention provides a simple modular surgical instrument to position an acetabular prosthesis into correct position, which rely upon specific parameters and specific mechanisms incorporated into the modular instrument in order to reduce the likelihood of malpositioning an acetabular prosthetic socket into a reamed acetabulum of pelvic bone.
A malpositioned acetabular prosthetic socket can lead to several complications such as, dislocation of the hip joint, impingement of the prosthetic elements, impingement of soft tissues, decreased joint motion, painful joint, limping, increased wear and tear of the prosthetic elements, and eventual loosening and failure of the implant.
Correct anatomical placement and implantation of acetabular prosthetic socket can be surgically demanding and challenging task for orthopaedic surgeons. Correct alignment and implantation is hampered by a deep wound, bleeding from the reamed bony acetabulum, few clear reference landmarks, major neurovascular structures, close to the operating field.
To prevent malpositioning of acetabular prosthetic socket, several surgical instruments and methods have been devoloped in the art, but many such instruments are limited in application at the time of a major surgical procedure.
Hip joint replacement surgery requires knowledge of topographical and surgical anatomy of patients and clinical pathology of the hip joint. Many currently available acetabular prosthetic socket alignment apparatus and methods, merely rely upon reference landmarks external to the pelvis of a patient, the reliance placed on such external landmarks on pelvis tend to introduce inadvertent misjudgements arising from the variations in patient""s external landmarks associated with obesity, patient""s position on the operating table, previous surgeries on the hip or pelvis, and surgeon""s proprioceptive skills, and the results can vary widely, wherein reliable and consistant results are not assured.
Instruments incorporating electronics, computer tomographic scans, intraoperative radiological monitoring, have been used to position an acetabular prosthetic socketc correctly, but then these instruments and methods can be expensive, complicated, invasive, again some of them can be misleading and are not widely practical, and are not widely popular.
2. Description of the Related Art
The following patents are related for positioning and implanting an acetabular prosthetic cup into acetabulum of a pelvic bone.
U.S. Pat. No. 4,305,394 to Bertuch Jr. (1981)
U.S. Pat. No. 4,475,549 to Oh (1984)
U.S. Pat. No. 4,994,064 to Aboczsky (1991)
U.S. Pat. No. 5,037,424 to Aboczsky (1991)
U.S. Pat. No. 4,141,512 to Farmer et al (1992)
U.S. Pat. No. 5,284,483 to Johnson (1994)
U.S. Pat. No. 5,320,625 to Bertin (1994)
U.S. Pat. No. 5,364,403 to Petersen (1994)
U.S. Pat. No. 5,540,697 to Rehmann (1996)
U.S. Pat. No. 4,716,894 to Lazzari (1998)
U.S. Pat. No. 6,214,014 BI to McGann (2001)
U.S. Pat. No. 6,395,005 BI to Lovell (2002)
For example U.S Pat. No. 4,305,394 to Bertuch Jr. discloses an acetabular prosthetic socket positioning instrument that has an interchangeable ball and a flange and a drive mechanism operatively connected through a drive coupling rod, flexible drive cable and drive member and carrying such ball. The instrument also discloses a left hand handle, a stabilising rod, a right hand handle and a L shaped hollow drive housing. Similarly, U.S. Pat. No. 475,549 to Indong Oh discloses an acetabular cup positioner, comprising a head having an axis which is receivable in the acetabular cup, a first arm coupled to the head and extending from the head at an acute angle, and a second arm coupled to the first arm at a location spaced from the head and the arms and the axis are coupled the first arm such that the antiversion angle can be established for the right and left hips by aligning the first and second hands, respectively with the patient axis.
U.S. Pat. No. 4,716,894 to Lazzeri et al; discloses an acetabular cup inserting instrument comprising a first handle and a second handle extending therefrom, the second handle is selectively locable in a desired position with respect to the first handle.
Instruments that address the orientation, inserting and impacting problems for acetabular prosthetic sockets are known in the art. For example U.S. Pat. No. 4,994,064 and U.S. Pat. No. 5,037,424 to Robert Aboczky discloses an instrument comprising an impaction rod, coupling rod, pivoting rod and supporting rod. Acetabular prosthetic cup is aligned and inserted in accordance with a plane normal to line between the right and left anterior iliac spines. The alignment arrangement includes a bar which is rotatably adjustable about the axis of coupling rod, and which is aligned normal to a line which crosses from posterior superior iliac to the anterior iliac spine. U.S. Pat. No. 5,141,512 to Malcom Fraser et al; discloses a modular apparatus for proper alignment of an acetabular prosthetic socket, includes a frame having feet which are placed against anterior iliac spines and symphysis pubis. The invention includes a light beam directed from a source through an aperture to a mirror mounted on an inserter. The light beam is reflected back from the mirror to a target region. When the incident and reflected beam are coincident the cup is aligned for correct placement. The target region is rotatably and pivotably mounted for precise adjustments of the angle of abduction and antiversion respectively. The instrument appear bulky, complicated and occupy considerable space at the time of surgery, and also appear not suitable for patients placed in lateral position.
U.S. Pat. No. 5,284,483 to Erin Johnson discloses an instrument comprising a first elongated handle, a second elongated handle extending therefrom. The second handle is capable of ratcheting about the longitudinal axis of the first elongated handle. The second handle may be selectively locked in a desired position with respect to the first handle by means of a control on the ratchet mechanism to aid proper positioning an acetabular prosthetic cup. Similarly U.S. Pat. No. 5,320,625 to Kim Bertin discloses an apparatus that includes a orientation bar and an alignment arm, laterally displaced from the longitudinal axis of the apparatus and selectively fixed or rotatably connected in order to implant the acetabular prosthetic cup in desired orientation.
Similarly U.S. Pat. No. 5,364,403 to Thomas Petersen discloses an instrument, provides a resilient collar at one end connecting the acetabular cup, a sighting guide and an A-shaped alignment guide to check the alignment of the acetabular cup with anatomical check points on the patient. Similarly apparatus U.S. Pat. No. 5,540,697 to Mark Rehmann discloses both axial and angular alignment references to fecilitate correct alignment of an acetabular prosthetic cup, the alignment includes an abduction indicating member and antiversion indicating member connected to an elongated tool body to provide an axial alignment guide.
U.S. Pat. No. 6,214,014 BI to William McGann discloses an alignment system for hip replacement surgery, the acetabular guide comprises of three components, the laser pointer, goniometer, and a swing arm. The swing arm includes a window with an alignment guide, the laser light is directed towards a wall in the operating room and a mark is made on the wall where the laser light points. The goniometer and the laser pointer are removed after appropriate mark is imdicated on the operating room wall. The acetabular cup is inserted with the aid of a handle and the handle is appropriately aligned by inserting the laser pointer into the bore and moving the handle until the laser light of the pointer is aligned with the previously indicated mark on the wall, and once this has occured the acetabular cup is finally inserted into the predetermined position. Again such system utilises a goniometer and laser light nonspecifically laser light pointing on to a wall, and is undesirably limited in application due to, for example variations associated with positioning of the patient on the operating table, shape of the wall, size of the wall, position of the operating table and other variables in the operating room at the time of surgery.
Similarly alignment methods and apparatuses that utilize natural landmarks available on pelvic bones to guide the alignment of an acetabular device in connection with the implant of a prosthetic hip joint at an implant site in the pelvis are known in the art. For example U.S. Pat. No. 6,395,005 BI to Timmothy Lovell discloses an acetabular alignment apparatus and method, the device includes a positioning shaft having a longitudinal axis and locators are mounted upon the positioning shaft for placement adjacent sellected landmarks on the pelvis to orient the shaft axis of a prepared acetabulum at the implant site in order to place the shaft axis at a prescribed angle of abduction and prescribed angle of antiversion thereby orienting the acetabular device at the appropriate angle of abduction and appropriate angle of antiversion.
Similarly the current positioning instruments to implant an acetabular prosthetic sockets mostly rely upon non-specific parameters such as: external reference landmarks on the patient, non-specific alignment bars, rods, shafts, pins, bolts and nuts, complicated attachments, direct observation of the prosthetic cup by the surgeon at the time of surgery, complicated ways of utilising laser beam, and time consuming parameters.
What is needed is an improved modular instrument to correctly position an acetabular prosthetic socket, wherein the instrument is simple to understand, simple to assemble, simple to use more accurately with precision, wherein the surgeon utilises the instrument faster with confidence at the time of surgery.
What is also needed a modular instrument that also provide a lavelling apparatus and a laser beam apparatus, desirable mathematical accuracy, that rely on specific dependable parameters.
The object of the present invention is to provide an acetabular prosthetic socket positioning instrument, an improved modular surgical instrument for correct positioning of the prosthetic socket in a reamed bony acetabulum of a patient, during a total hip joint replacement surgical procedure. The present invention provides a simple modular instrument, easy to assemble, easy to understand and versatile in application. The present invention provides an improved and reliable modular instrument which can be used to establish the correct abduction and antiversion angles of the acetabular prosthetic socket, by aligning the alignment shaft, the orientation pillar, the levelling apparatus and the laser pen apparatus.
In one form thereof, the present invention provides a hemispherical ball member, adapted to cooperate with an acetabular prosthetic socket and an alignment shaft having an intermediate shank, a distal handle and an impaction knob. The lower end of an orientation pillar is coupled and anchored into the shank of the alignment shaft at an oblique angle of 135 degrees. The upper end of orientation pillar is incorporated with a levelling apparatus, and the intermediate part of orientation pillar is incorporated with a laser pen apparatus.
In preffered form, the proximal end of the modular instrument comprises of hemispherical ball member having an outer convex surface adapted to cooperate with the acetabular socket. In a preffered form of the invention, the inner flat surface of the hemispherical ball member further comprises of a threaded pit disposed in the center of the flat surface. More preferably, the proximal end of the alignment shaft is adapted to have threaded means, and the connection between the hemispherical ball member and the alignment shaft is through a threading mechanism.
More preferably, the hemispherical ball member is detachably attached to the proximal end of the alignment shaft by means of corresponding threads.
In a preffered form, the modular acetabular prosthetic socket positioning instrument further comprises of a levelling apparatus incorporated into the upper end of orientation pillar, is to establish correct abduction angle of the acetabular prosthetic socket in the acetabulum.
In a preffered form, the modular instrument further comprises of a laser pen apparatus, incorporated at an intermediate location in the orientation pillar, is to establish correct antiversion and retroversion angles of the acetabular prosthetic socket in the acetabulum.
In another form thereof, the present invention provides a modular instrument for custom fitting an acetabular prosthetic socket to individual patient, in this method the hemispherical ball member is sellected from a plurality of different hemispherical ball members, depending on the inner size of an acetabular prosthetic socket to be implanted into the reamed bony acetabulum.
In a preffered form of the invention, the orientation pillar member is coupled and anchored to the alignment shaft at an oblique angle of 135 degrees at an intermediate location in the shank, to the horizontal axis of the alignment shaft.
In one form thereof, the orientation pillar comprises of a levelling apparatus incorporated at its distal end. The levelling apparatus further consists of a semitubular bar member and a tubular level bit. The level bit member is detachably installed into the semitubular bar member, with click-in and click-out method.
In another form thereof, the present invention also provides a laser pen apparatus for custom fitting a prosthetic socket in desired position of antiversion or retroversion as the case may require. In this laser pen apparatus, a semitubular arm member is coupled to the orientation pillar member with
-a hinge mechanism. A laser pen is detachably installed into the semitubular arm member so that the laser beam directed towards the hemispherical ball member. The hinge mechanism of the semitubular arm member permit up and down movement of semitubular arm member and the laser pen and to focus the laser beam on to the patient""s predetermined anatomical landmarks on the boney pelvis.
In a preffered form of the present invention, the semitubular bar member is permanently attached at the center of its convex surface, equal length on either side, to the center of the distal end of orientation pillar, means, the semitubular member is placed perpendicular to the longitudinal axis of orientation pillar.
In a preffered form of the present invention, the air bubble in the level bit cooperate with the semitubular bar, with the orientation pillar and the alignment shaft to position and implant acetabular prosthetic socket into correct abduction angle of 45 degrees or desired anatomical position in the reamed acetabulum.
One advantage of the present invention is easy to assemble the hemispherical ball member into the alignment shaft, to cooperate with the acetabular prosthetic socket to be implanted into the patient""s acetabulum.
One advantage of the present invention is easy to assemble the level bit into the semitubular bar member of the levelling apparatus.
Yet another advantage of the present invention is easy to assemble the laser pen into the semitubular arm member of the laser pen apparatus
Yet another advantage of the present invention is easy to manoeuver the modular instrument to correctly position an acetabular prosthetic socket, by using the hemispherical ball member, the alignment shaft member, and the orientation pillar by utilising the more accurate methods of assessment incorporated into the levelling apparatus and into the laser pen apparatus.
Yet another advantage of the present invention is simple and easy application and saves much needed time for the surgeon at the time of surgery.
Yet another advantage of the present invention is provide confidence to the surgeon and the training staff for correct implantation of an acetabular prosthetic socket during hip joint replacement surgery.
While pre-operative imaging techniques and intra-operative imaging techniques and complicated instruments can be used to determine the abduction angle, antiversion angle, adduction angle, retroversion angle of a particular patients acetabulum, such techniques are often only an approximation, and are difficult to interpret during the actual surgical procedure in the operating room, wherein the surgical wound is deep, where the reamed acetabulum is oozing blood and obscures the acetabulum, wherein the operating time is constrained due to old age of the patients, and also where the normal anatomy of the patient is distorted due to advanced asteoarthritis or other pathological process and also where the neurovascular structures are close to the operating field.
The present invention provides the necessary adjustments in various angles of abduction, adduction, antiversion, and retroversion, at the time of a major hip joint replacement surgical procedure. The inventive modular instrument can prevent several intra-operative and post-operative complications associated with malpositioning of an acetabular prosthetic socket.